CH4＞NH3＞H2O＞HF；第三周期：SiH4＞PH3＞H2S＞HCl．（2）化合物的毒性：PH3＞NH3；&H2S＞H2O；&CS2＞CO2；&CCl4＞CF4于是科学家们开始把注意力集中在含F、Cl的化合物上．（3）已知CCl4的沸点为76.8°C，CF4的沸点为-128°C，新的致冷剂的沸点范围应介于其间．经过较长时间反复试验，一种新的致冷剂氟里昂CF2Cl2终于诞生了，其他类似的还可以是CFCl3或CF3Cl．已知甲烷是正四面体结构，则CF2Cl2无（填有或者无）同分异构体．（4）然而，这种致冷剂造成了当今某一环境问题是破坏臭氧层，但求助于周期表中元素及化合物的①②③（填写序号）变化趋势来开发致冷剂的科学学维方法是值得借鉴的．①毒性②沸点③易燃性④水溶性⑤颜色．
科目：高中化学
致冷剂是一种易被压缩、液化的气体，液化后在管内循环，蒸发时吸收热量，使环境温度降低，达到致冷目的．人们曾采用过乙醚、NH3、CH3Cl等作致冷剂，但它们不是有毒，就是易燃、于是科学家根据元素性质的递变规律来开发新的致冷剂据现有知识，某些元素化合物的易燃性、毒性变化趋势如下：（1）氢化物的易燃性：第二周期CH4＞NH3＞H2O＞HF；（2）化合物的毒性：PH3＞NH3；&H2S＞H2O；CCl4＞CF4&&（选填＞或＜）．（3）已知CCl4的沸点为76.8℃，CF4的沸点为-128℃，新致冷剂的沸点范围应介于其间．经过较长时间反复试验，一种新的致冷剂氟里昂CF2Cl2终于诞生了，其它类似于CF2Cl2的物质还可能有CFCl3（或CClF3）．（填一种）；这类致冷剂的大量使用造成了当今的某一环境问题是臭氧层空洞&（选填：温室效应、酸雨、臭氧层空洞、光化学烟雾）．（4）根据周期表中元素及其化合物的a变化趋势来开发致冷剂的科学思维方法是值得借鉴的．（填写字母，多选扣分）①毒性&&②沸点&&③易燃性&&④水溶性&&⑤颜色　　　（a）①②③（b）②④⑤（c）②③④
科目：高中化学
致冷剂是一种易被压缩、液化的气体，液化后在管内循环，蒸发时吸收热量，使环境温度降低，达到致冷目的。人们曾采用过乙醚、NH3、CH3Cl等作致冷剂，但它们不是有毒，就是易燃，于是科学家根据元素性质的递变规律来开发新的致冷剂。? 据现有知识，某些元素化合物的易燃性、毒性变化趋势如下：?（1）氢化物的易燃性：第二周期__________＞__________＞H2O＞HF；第三周期 SiH4＞PH3＞__________＞__________。（2）化合物的毒性：PH3＞NH3；H2S__________H2O；CS2__________CO2；CCl4＞CF4（选填“＞”“＜”或“＝”）。于是科学家们开始把注意力集中在含F、Cl的化合物上。（3）已知CCl4的沸点为76.8 ℃，CF4的沸点为－128 ℃，新致冷剂的沸点范围应介于其间。经过较长时间反复试验，一种新的致冷剂氟利昂CF2Cl2终于诞生了，其他类似的还可以是____________________。（4）然而，这种致冷剂造成了当今的某一环境问题是__________________。但求助于周期表中元素及其化合物的__________变化趋势来开发致冷剂的科学思维方法是值得借鉴的。①毒性②沸点③易燃性④水溶性⑤颜色?（a）①②③（b）②④⑤（c）②③④?
科目：高中化学
致冷剂是一种易被压缩、液化的气体，液化后在管内循环，蒸发时吸收热量，使环境温度降低，达到致冷目的。人们曾采用过乙醚、一氯甲烷等作致冷剂，但它们不是有毒，就是易燃。于是科学家根据元素性质的递变规律来开发新的致冷剂。据现有知识，某些元素化合物的易燃性、毒性变化趋势如下：(1)氢化物的易燃性第二周期：____________＞_____________＞H2O＞HF第三周期：SiH4＞PH3＞______________＞_____________(2)化合物的毒性PH3＞NH3& H2S______________H2O& CS2______________CO2(填“＞”或“＜”)于是科学家们开始把注意力集中在含F、Cl的化合物上。(3)已知CCl4的沸点为76.8 ℃，CF4的沸点为-128 ℃。新致冷剂的沸点范围介于其间。经过较长时间反复试验，一种新的致冷剂氟利昂(CCl2F2)终于诞生了，此外其他类似的还可以是_________________。(4)然而，这种致冷剂造成了当今的某一环境问题是_________________。但求助于周期表中元素及其化合物的___________________变化趋势来开发致冷剂的科学思维方法是值得借鉴的(填写字母)。①毒性& ②沸点& ③易燃性& ④水溶性& ⑤颜色a.①②③&&&&&&&&&&&&&&&&&&& b.②④⑤&&&&&&&&&&&&&&&&& c.②③④
科目：高中化学
致冷剂是一种易被压缩、液化的气体，液化后在管内循环，蒸发时吸收热量，使环境温度降低，达到致冷目的。人们曾采用过乙醚、NH3、CH3Cl等作致冷剂，但它们不是有毒，就是易燃，于是科学家根据元素性质的递变规律来开发新的致冷剂。 据现有知识，某些元素化合物的易燃性、毒性变化趋势如下：(1)氢化物的易燃性：第二周期________＞________＞H2O＞HF；第三周期 SiH4＞PH3＞________＞________。(2)化合物的毒性：PH3＞NH3；H2S________H2O；CS2________CO2；CCl4________CF4(选填＞、＜或＝)。于是科学家们开始把注意力集中在含F、Cl的化合物上。(3)已知CCl4的沸点为76.8 ℃，CF4的沸点为-128 ℃，新致冷剂的沸点范围应介于其间。经过较长时间反复试验，一种新的致冷剂氟利昂CF2Cl2终于诞生了，其他类似的还可以是_________。(4)然而，这种致冷剂造成了当今的某一环境问题是___________________。但求助于周期表中元素及其化合物的__________变化趋势来开发致冷剂的科学思维方法是值得借鉴的。(填写字母)①毒性　②沸点　③易燃性　④水溶性　⑤颜色a.①②③&&&&&&&&& b.②④⑤&&&&&&&&&& c.②③④
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Spontaneous electric fields in films of CF3Cl, CF2Cl2 and CFCl3
Corresponding authors
Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Institute for Storage Ring Facilities (ISA) and Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Data are presented showing the spontaneous formation of electric fields within solid films of the chlorofluorocarbons (CFCs) CF3Cl, CF2Cl2 and CFCl3 as a function of film deposition temperature from 40 K and above. Electric fields, which arise through dipole alignment and lie in the range of a few times 107 V m-1 to a few times 106 V m-1, decrease as the degree of chlorination increases. Maximum deposition temperatures for display of an electric field lie at ~50 K, ~65 K and ~52 K for CF3Cl, CF2Cl2 and CFCl3 respectively. CFCl3 films possess electric fields which show an onset of temporal metastability between deposition temperatures of 46 K and 50 K. CF3Cl and CF2Cl2 demonstrate temperatures of ~65 K and ~80 K at which the electric field in the film is removed by heating, so-called Curie points, with decay of the field spread over more than 10 K. CFCl3 displays a comparatively sharp Curie point at 55 K. This variety of behaviour arises despite the resemblance of these three species in terms of electronic structure and gas phase dipole moment, emphasising the requirement for detailed chemical models of this phenomenon.
The article was
received on 07 Sep 2012,
accepted on 23 Oct 2012
first published on 24 Oct 2012
Article type:
Phys. Chem. Chem. Phys., 2013,15, 108-113
ReferenceManager
A. Cassidy, O. Plekan, R. Balog, N. C. Jones and D. Field,
Phys. Chem. Chem. Phys., 2013,&15, 108
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